1. Field of the Invention
The present invention relates to a tubular elastic linkage device for axle beam that elastically links an end of an axle beam to a truck frame of a railway vehicle.
2. Description of the Related Art
From the past, railway vehicles generally employ a structure wherein an axle beam extends out in the vehicle longitudinal direction from an axle box part that supports an axle, and an end of the axle beam is elastically linked to a truck frame by a tubular elastic linkage device. As Japanese Unexamined Patent Publication No. JP-A-2014-020487 and the like disclose, this tubular elastic linkage device for axle beam comprises an inner axial member, a pair of outer segments disposed about radially outward of the inner axial member so as to extend in the circumferential direction, and a main rubber elastic body elastically connecting the inner axial member and the pair of outer segments to one another. Both axial ends of the inner axial member are fixed to the truck frame, while the outer segments are attached to a tubular housing part provided at an end of the axle beam. By so doing, the axle beam is elastically supported by the truck frame via the tubular elastic linkage device for axle beam.
The tubular elastic linkage device for axle beam may be provided with a stopper, in order to limit relative displacement between the inner axial member and the pair of outer segments in a specified radial direction in which a large load input is expected. Specifically, since a large load during deceleration is input upon the tubular elastic linkage device for axle beam in the radial direction corresponding to the vehicle longitudinal direction, in JP-A-2014-020487, the stopper is provided protruding from the inner axial member toward either of the outer segments in the radial direction. The inner axial member and the outer segment come into contact via the stopper, thereby limiting the relative displacement between the inner axial member and the outer segments in the specified radial direction. This arrangement provides improvement of durability of the main rubber elastic body, the target braking performance of the railway vehicle, and the like.
According to JP-A-2014-020487, the stopper is disposed radially between the face of the inner axial member and the face of the corresponding outer segment that face each other, and the main rubber elastic body is provided continuously between the stopper and the outer segment. With this structure, unfortunately, not only in a large load input, but also for normal vibration between the truck and the axle that is input during drive etc., the main rubber elastic body is compressed in a narrow part between the faces of the stopper and the outer segment in the radial direction where the stopper is disposed. As a result, the spring characteristics of the device get harder and adversely affect suspension performance of the truck. Moreover, in the structure of JP-A-2014-020487, the main rubber elastic body provides linkage between the stopper and the outer segment. Therefore, when a load in the circumferential direction is input between the inner axial member and the outer segment of the tubular elastic linkage device, the main rubber elastic body is compressed by the stopper, thereby exerting hard spring. This hard spring is likely to affect suspension characteristics of the truck.
In Japanese Patent No. JP-B-3747783, there is proposed a structure wherein a gap is provided between the stopper and the housing part such that the stopper supported by the inner axial member touches the housing part only during a large load input. In JP-B-3747783, the pair of outer segments are disposed to face each other in the vertical direction. The stopper is disposed between the circumferential ends of the upper and lower outer segments, whereby the protruding tip of the stopper and the outer segments are not radially linked by the main rubber elastic body, while a prescribed gap is formed on the side of the protruding tip of the stopper.
Unfortunately, for the above-referenced structure wherein the gap is formed radially between the stopper and the housing part, the rubber volume of the main rubber elastic body is small in the radial direction where the stopper is disposed. Therefore, in the radial direction, the spring constant is likely to be smaller than in another radial direction, so that the degree of freedom in tuning the characteristics may become small in the normal vibration input state like the time of driving.
Since the outer segments are disposed to face each other in the vertical direction, if they are attached to the housing part of division structure in the vehicle longitudinal direction as shown in FIG. 13 of JP-B-3747783, outer peripheral faces of the outer segments may be damaged by galling by the division edges of the housing part, or the like. If the special structure as shown in JP-B-3747783 is not used, it is required to perform attachment works of the device to the axle beam carefully.